The following systems rely on the bleed air
system for operation:
  • Air conditioning/pressurization
  • Wing and engine thermal anti-icing
  • Engine starting
  • Hydraulic reservoirs pressurization
  • Water tank pressurization
B737-800/900  Bleed Air System

Air for the bleed air system can be supplied by
the engines, APU, or an external air cart/source.
The APU or external cart supplies air to the
bleed air duct prior to engine start. After engine
start, air for the bleed air system is normally
supplied by the engines.
Air Systems SGR